1. Field of Invention
The present invention relates to a machinery for packaging which is used in food and pharmaceutical industries, and more particularly to a sterilizer and dryer device for food and pharmaceutical industries.
2. Description of Related Arts
In food and pharmaceutical packaging machinery industries, uniformity of heat to flow is an important index for research in sterilizer and dryer device which utilizes circulating hot air. The heating principle is carrying out heat exchange through a heater and a circulating air flow. The circulating air is first heated by the heater, guided to flow into a wind shield and to a high temperature high efficiency filter device, and then having heat exchange with food or pharmaceutical bottle. Generally, the control method includes one temperature probe positioned in the middle of a heating chamber of the oven which is used as the point of control to detect the temperature of air flow at a lower level of the heating chamber and to provide a feedback to a control unit. The control unit then controls the amount of heat from the heater to control the temperature of the air flow. However, when the capacity requirement is increased, a length of the tunnel type oven is increased. Accordingly, the provision of only one point in the middle of the heating chamber fails to effectively control the temperature of the entire heating surface in the heating chamber. Therefore, problem of over-heat is common for the conventional oven. Also, temperature difference between a front and a back portion of the heating chamber not only affects the uniformity of temperature, but also has a direct impact on the functionality of the device. When the temperature is too high, parts of the heating chamber may be damaged (for example, the high temperature high efficiency filter usually has a maximum temperature threshold of operation).